Test bed comprising elastic connector elements for helicopter gearboxes

ABSTRACT

A testing stand for a helicopter transmission is arranged in a testing stand ( 20 ) capable of swiveling deflection around a rotor shaft ( 4 ) with one output side rotor shaft ( 4 ) and at least one drive side input shaft ( 6, 8 ). Actuators ( 28, 30 ) are provided around the rotor shaft axis ( 4 ) for swiveling deflection of the helicopter transmission ( 2 ) to equalize shifts on connection couplings ( 14, 16, 22 ) occurring under load. It is suggested that the helicopter transmission ( 2 ) be clampable in the testing stand ( 20 ) by connection elements ( 24, 26 ) elastic with respectable to swiveling deflection.

[0001] The invention concerns a testing stand for helicopter transmissions with features according to the preamble of claim 1.

[0002] Helicopter transmissions branch drive outputs of one to three drive machines at torque reductions to various outputs, such as main rotor, tail rotor and auxiliary outputs. These specifically highly stressed transmissions are constructed small and light in accordance with the demands in air travel. The transmission housings are chiefly made of aluminum and magnesium alloys. The elasticity modules of these materials lie at one half to one third of the elasticity module of steel alloys. That is, the elastic deformations lie correspondingly higher under load. In particular, a twisting of the transmission housing occurs about the rotor shaft axis.

[0003] As a consequence, inputs and outputs that are arranged at a radial distance from the rotor shaft axis on the transmission shift out of their original position. Distortions and radial shifts occur on the axes of the inputs and outputs of the transmissions in relation to the axes of connectable shafts which lead to the drive machines or to the tail rotor output.

[0004] A portion of the shifts is equalized by torsionally rigid, angularly mobile disc or membrane clutches. A considerable portion of the shifts is nonetheless equalized by the as a rule very long connection shaft to the drive machines or to the tail rotor output.

[0005] For testing a helicopter transmission on a testing stand, the installation situation of the helicopter transmission in the helicopter airframe is largely simulated. Nonetheless, basically shorter drive and output shafts are used in testing stand construction for reasons of space. A greater part of the shifts must be equalized by the clutch elements owing to the shorter shafts. In addition to a basically higher load on the clutch elements due to the greater angles, essentially higher bearing stresses also occur in a radial direction on the inputs and outputs of the helicopter transmissions. The high loads at simultaneously very high rotational speeds up to approximately 25,000/min. can lead to breakage of the clutch elements and to damage in the bearing region of the input and output shafts and on the highly sensitive free wheelings of the helicopter transmissions. Very high stresses upon the components of the testing stand result from this which go beyond the operating loads in the helicopter and, in the worst case, can cause preliminary damage to the transmission.

[0006] DE 198 22 093 A1 discloses a testing stand for helicopter transmissions in which a clamping plate that can be rotated by at least one actuator about the rotor shaft axis of the test transmission is provided for accommodating the helicopter transmission. The actuators are activated in a load-dependent manner to compensate for shifts arising under load on the connection clutches of the helicopter transmission.

[0007] The clamping plate and its bearing are nonetheless relatively expensive. The invention is, therefore, based upon indicating a more economical suspension of the test transmission with which an equalization of shifting is nonetheless possible.

[0008] This objective is accomplished in that the helicopter transmission can be clamped using elastic connection elements with reference to the swiveling deflection in the testing stand. Since the necessary angle shifts are only a few degrees, a sufficiently large amount of swiveling deflection is already made possible through the elastic swiveling elements.

[0009] In an advantageous refinement of the invention, the testing stand has a central connection member beneath the helicopter transmission from which at least two elastic connection elements extend radially outward on the outer ends of which an actuator is respectively articulated, and on the outer ends of which moreover fastening points for accommodating the helicopter transmission are situated. Since the elasticity is only desired in the direction of the swiveling deflection, but otherwise the connection elements should be suited to accommodate forces without deformation, it is advantageous if the elastic connection elements have a high elasticity solely with regard to the swiveling deflection.

[0010] The invention will be explained in greater detail on the basis of the appended Figures, wherein:

[0011]FIG. 1 illustrates a schematic plan view; and

[0012]FIG. 2 illustrates an elevation of the testing stand of the invention.

[0013] The helicopter transmission to be tested is designated with 2 in FIG. 1, a rotor shaft axis 4 runs perpendicular to the drawing plane. The helicopter transmission 2 has several inputs and outputs. The driving connection shafts to a testing stand are designated with 6 and 8 which are coupled on inputs 10, 12 using connection couplings 14, 16 to the helicopter transmission. The input shafts 6, 8 run, just as the tail rotor output shafts 18, basically on a place orthogonal toward the rotor shaft axis 4.

[0014] An installation frame 20 accommodates the transmission. The housing of the helicopter transmission is deformed under load so that harmful angle shifts would arise on connection couplings 14, 16, 22 to the input or output shafts 6, 8, 18. In order to prevent this, the helicopter transmission is arranged in the installation frame 20 of the testing stand swiveling deflectably using elastic connection elements 24, 26, whereby the helicopter transmission is rotated on its suspension about a equalizing angle by actuators 28, 30 in a load-dependent manner so that the angle shifts on the connection couplings 14, 16, 22 are equalized.

[0015] The manner in which the helicopter transmission is clamped in the installation frame 20 is most apparent on the basis of FIG. 2. The installation frame 20 has a central connection member 34 coaxial in relation to the rotor shaft axis 4 which is rigidly connected with the installation frame 20. The elastic elements 24, 26 constructed as diaphragms are installed on the central connection member 34. An actuator 28, 30 is respectively articulated in the region of the outer end of these elastic connection elements 24, 26. Moreover fastening points 36, 38 are provided in the region of the outer end for accommodating the helicopter transmission.

[0016] Of the helicopter transmission, only a so-called torque-reacting plate 40 is illustrated in FIG. 2, which also accommodates the reaction factors of the helicopter transmission housing in the helicopter under load and transmits them to the helicopter airframe or the testing stand. The helicopter transmission housing (not represented in FIG. 2) is fastened to the torque-reacting plate 40 using a circular series of bolts 42.

[0017] The elastic elements 24, 26 have a rectangular cross section with less thickness and greater height so that they have a high elasticity only in relation to the swiveling deflection of the helicopter transmission. The fastening sheets 44, 46 installed on the elastic elements 24, 26 have first of all the fastening points 36, 38 for the torque-reacting plate 40 and lie at the same time on the installation frame 20 so that they slide with a swiveling deflection of the installation frame 20 and thereby stabilize the entire device.

REFERENCE NUMERALS

[0018]2 helicopter transmission

[0019]4 rotor shaft axis

[0020]6 shaft

[0021]8 shaft

[0022]10 input

[0023]12 input

[0024]14 connection coupling

[0025]16 connection coupling

[0026]18 shaft

[0027]20 installation frame

[0028]22 connection coupling

[0029]24 elastic connection element

[0030]26 elastic connection element

[0031]28 actuator

[0032]30 actuator

[0033]34 central connection member

[0034]36 fastening point

[0035]38 fastening point

[0036]40 torque-reacting plate

[0037]42 series of bolts

[0038]44 fastening sheet

[0039]46 fastening sheet 

1. Testing stand for helicopter transmissions (2) with an output side rotor shaft (4) and at least one drive-side input shaft (10, 12) which can be connected transmission-wise by shafts (6, 8) and connection couplings (14, 16, 22) with at least one testing stand side shaft connection, whereby the helicopter transmission (2) is arranged capable of swiveling deflection about the rotor shaft axis (4), whereby at least one actuator (28, 30) is provided for swiveling deflection of the helicopter transmission (2) about its rotor shaft axis (4) in order to equalize shifts on the connection couplings (14, 16, 22) of the helicopter transmission (2) occurring under load, wherein the helicopter transmission (2) can be clamped in the testing stand (20) by connection elements (24, 26) elastic with relation to swiveling deflection.
 2. Testing stand according to claim 1, wherein the testing stand has a central connection member (34) underneath the helicopter transmission (2) from which at least two elastic connection elements (24, 26) extend radially outward on the outer ends of which respectively one actuator (28, 30) is articulated and on which the fastening points (36, 38) for accommodating the helicopter transmission (2) are found.
 3. Testing stand according to claim 1 or 2, wherein the elastic connection elements (24, 26) have high elasticity only in relation to swiveling deflection. 